Vehicle Anatomy & Science

Question 1

What are the 4 classifications of vehicles?

Answer 1

• Passenger cars
• Light duty trucks
• Medium and heavy duty trucks - designed for hauling cargo and specialty chassis applications. Examples include construction vehicles and fire trucks.
  
  • Medium duty trucks: 13,000 - 33,000 GVW
  • Heavy duty trucks: over 33,000 GVW
• Buses and specialty vehicles - includes agricultural equipment

Question 2

What are some hazards associated with heavy equipment?

Answer 2

• Harder to stabilize
• Special cargo
• Crush injuries
• Pinch points
• Rollover entrapment
• Potential and kinetic energy

Question 3

What are the 8 sides to every vehicle?

Answer 3

• Front
• Rear
• Interior
• Exterior
• Driver’s side
• Passenger’s side
• Undercarriage
• Roof

Question 4

How are door/roof posts identified in a vehicle?

Answer 4

The structural members that surround the doors and support the roof of a vehicle are identified alphabetically from the front to rear (i.e. A-post, B-post, C-post, etc.).

Question 5

How strong are the posts of a vehicle?

Answer 5

The posts in a vehicle have to hold 1.5 times the weight of the car.

Question 6

What materials are used to construct cars?

Answer 6

• Steel
• Aluminum
• Magnesium
• Plastic
• Carbon fiber
• Copper
• Cast iron
• Composite materials
• Alloys
• Glass

Question 7

What is a firewall or bulkhead?

Answer 7

A partition between the engine compartment and the passenger compartment of a vehicle designed to protect occupants from the engine and its associated hazards.

Question 8

What is a dashboard support system?

Answer 8

A safety feature that prevents the dashboard from collapsing onto occupants during front impact collisions. It’s comprised of a metal bar that connects the A posts from driver’s side to passenger side.

Question 9

What hazard does magnesium pose?

Answer 9

It reacts with water! When water is applied to vehicle fires as an extinguishing agent, components made with magnesium can cause high heat fires. These components include:
* Mag wheels
* Valve covers
* Steering columns
* Mounting brackets on antilock bracking systems
* Transmission casings
* Engine blocks
* Frame supports
* Exterior body components

Question 10

What determines the structural integrity of a vehicle?

Answer 10

It’s frame.

Question 11

What is a chassis?

Answer 11

The basic operating system of a motor vehicle. It consists of the frame, suspension system, wheels, and steering mechanism.

Question 12

What is the concept of dual tools?

Answer 12

Always using two tools during rescue operations so that if one fails, there’s a backup in place for safety.

Question 13

What are the 3 types of vehicle frames?

Answer 13

• Full or rigid - the vehicle’s body attaches to a rigid frame (AKA “body-on-frame”). These are least affected by collision and can be found on larger vehicles such as trucks that pull heavy loads.
  
  • This design has been around since the creation of vehicles
  • Accommodates body style changes without having to reengineer the frame
  • There is a full frame from bumper to bumper
  • Applies to any vehicle with a chrome bumper and buses / trucks
  • If a body-on-frame vehicle is on it’s side and the frame is intact then you can use the frame to stabilize it.
• Unibody - a method of vehicle construction in which the frame and body are built as one unit instead of attaching the body to a frame; used in most modern cars.
  
  • Also known as “unitized body” or “integral frame”
  • The vehicle’s stress bearing elements and sheet metal body parts are built together as one unit
  • “Truss roof vehicle” - taking the roof off when it’s rolled over on it’s side is very dangerous
  • No support rails
  • Used for sports cars (i.e. Mustangs, Corvettes, etc.)
• Space - aluminium skeletons that are similar to aircraft frames upon which the aluminum, plastic, or composite skin of the vehicle’s body is attached. The internal structure of space frames provides the structural support for the vehicle while the skin provides aerodynamics, styling, and protection from the elements.
  
  • “Bird cage” configuration
  • Engine is connected to bird cage
  • AKA a “3 piece car”
  • Designed to support the entire load of the vehicle even if the outer skin is damaged
  • Lighter than body-on-frame (up to 50% less weight)
  • Designed for performance and fuel efficiency
  • Stabliize these cars on the posts

Question 14

What is the most common type of frame used in vehicle construction today?

Answer 14

Unibody

Question 15

What is a subframe?

Answer 15

The subframe is the structure below the frame that supports the axle, suspension, and powertrain. It serves to distribute heavy loads and isolate vibrations.
* ESP - electronic stability program
* Sensors in suspension
* Can drop the car up to 2 inches

Question 16

What is the main restraint in a vehicle?

Answer 16

The windshield. Note that this is also a structural component in many cars, so it’s no longer standard procedure to remove it.

Question 17

What is the standard for airbag placement in cars?

Answer 17

There is no standard!

Question 18

At what speed do airbags deploy?

Answer 18

Typical speed is from 100 - 200 mph!

Question 19

What is the concept of “clear before you cut”?

Answer 19

Undeployed airbags, seat belt pretensioners, and the pressurized gas cylinders that power them all pose a risk to rescuers when performing extrication since these can explode if punctured. Therefore rescuers must “peak and peel” throughout the trim of the vehicle to identify these hazards and mark them on the outside of the vehicle to ensure that cuts are made around them.

Question 20

What is the typical pressure of a pressurized gas cylinder for an airbag or seat belt pretensioner in a car?

Answer 20

These pressures are typically 4,000 psi but may be up to 11,400 psi in some cases.

Question 21

What color wires are usually associated with airbag systems?

Answer 21

Red, blue and yellow (orange is used for high voltage wires in electric vehicles)

Question 22

What is the correct way to cut a seatbelt?

Answer 22

At an angle at each end in the fully extended position (remember to save them since they can be used for multiple purposes)

Question 23

What energy absorbing features can be lethal hazards to extrication?

Answer 23

Compressed gas struts in which the gas and fluid inside the strut becomes overheated during a vehicle fire can result in an explosion of the strut assembly, launching a projectile that can cause serious injury to first responders. They are found in hoods, rear lift gates, trunks, third-row seats, camper shell hatches, toolboxes and other similar applications. They are used to prevent a door or hood from slamming shut under its own weight and to assist in holding the door open.

Struts consist of a hollow cylinder with a smaller solid metal rod or piston that slides inside. They are filled with an inert gas (usually nitrogen) and a small amount of oil and sealed where the solid rod exits the cylinder. When the strut assembly is subjected to fire, the gas expands, and the seal fails. The rod can become a missile, being launched with explosive force, damaging anything in its path.

Note that struts are a structural component of most modern independent suspension systems and serve as a connection point between the wheel and the vehicle body. They are mounted at the top of the chassis at the front-end of most front-wheel-drive vehicles. However, struts are not limited to front-wheel-drive configurations. The primary purpose of the struts is to support the weight of the vehicle while also absorbing surface impacts and ensuring a smooth ride. A strut assembly consists of two primary elements: the coil spring, which supports the height, weight and stability of the vehicle; and the shock absorber, which swallows bumps and dampens vibrations caused by irregularities on the roadway.

Question 24

What are the 4 types of glass used in cars?

Answer 24

• Laminated - this safety glass consists of two sheets of glass bonded to a piece of plastic in between them. This is most commonly used for windshields and some rear windows.
  
  • Impact produces many long, pointed shards with sharp edges, but the plastic sheet holds most of them in place.
  • Given that the glass remains attached to the plastic, it moves as a unit, which makes removal easier
  • Also known as “gorilla glass”
  • Black shading applied around the perimeter of the window indicates that it’s laminated
  • Note that you can remove laminated side windows with a halligan bar by piercing and pulling up and out
  • Best tool for breaking this type of glass is a glass saw / cutter such as the Rhino tool
• Tempered - designed to spread small fracture lines throughout the plate when struck. The glass separates into small pieces, decreasing the hazards of long, pointed pieces of glass. However, problems are created as small nuisance lacerations to unprotected body parts and the possible contamination of open wounds and eyes with tiny bits of glass.
  
  • Most commonly used in side windows and some rear windows
  • Best tool for breaking this type of glass is a spring loaded center punch
• Polycarbonate
• Transparent Armor
  
  • Lexon

Question 25

What are the two types of car battery systems?

Answer 25

1. Wet
2. Dry

Question 26

How has fuel tank construction changed over time?

Answer 26

They used to be made of aluminum or coated steel but modern models are made of plastic.

Question 27

Where can car batteries be located?

Answer 27

Everywhere except under the driver’s seat. For example:
* Under hood
* Trunk
* Rear seat
* Wheel well

Question 28

How do you disconnect the car battery?

Answer 28

Once the vehicle is stabilized and the ignition is turned off, cut the 12-volt battery cables. Cut the black (negative) first and then the red (positive). Be sure that the cables are double cut so the memory in the cable does not bring them back into contact.

Note that if it’s an electric vehicle, you must also use the emergency disconnect (if so equipped).

Note also that when disconnecting battery, you should always remove fuses whenever possible because of the chance of auxiliary power sources for airbags and other safety systems.

Question 29

What are pyrotechnic seat belt pretensioners?

Answer 29

A pretensioner is designed to retract some of the webbing of a seatbelt the instant a collision occurs, tightening the seatbelt to restrain occupants quickly and reducing the amount they are thrown forward in a moderate or severe frontal crash. The buckle pretensioner uses a pyrotechnic gas generator to propel a piston that is attached to the safety belt buckle with a cable. The cable pulls the buckle down toward the seat tightening the belt.

Question 30

Why are exhaust systems potentially dangerous to rescuers?

Answer 30

They’re hot and can burn you

Question 31

How does a vehicle’s center of gravity affect stabilization?

Answer 31

A vehicle’s center of gravity (COG) acts as a pivot point. The higher the COG the more susceptible the vehicle is to rollover. In contrast, the heavier the vehicle the more likely it is to settle towards the stability of the ground. Note that cargo will change a vehicle’s COG!

Question 32

Which types of vehicles have 12- versus 24-volt electrical systems?

Answer 32

Passenger vehicles and light duty trucks usually have 12-volt systems while larger trucks, recreational vehicles, and military vehicles operate on 24-volt systems.

Question 33

What are high-intensity discharge (HID) headlights?

Answer 33

An alternative to conventional headlights that use an inert, highly pressurized xenon gas to produce a slightly bluish-looking light that is up to 3 times brighter than common halogen headlights.

Question 34

What 5 passenger safety systems are found in cars?

Answer 34

1. Seatbelts
2. Supplemental passenger restraint systems (SPRP) - airbags
3. Side-impact protection systems (SIPS) - side curtain airbags
4. Head protection systems (HPS) - airbags that deploy from just above the door frame
5. Roll over protection system (ROPS) - this is a rollover bar that’s located behind the front seat in a sports car and deploys automatically during rapid acceleration or roll over